The first problem is that you have two of the most complex films stars played by amateurs. Let's take a look at Ms. Lohan first. Lindsey Lohan and Elizabeth Taylor have had similar lives. Like Taylor Lohan was a child star who may have grown up too quickly, thus preventing her from understanding normal. There is a line in the film where Taylor takes time off from the movies (at age 29) and states I have made 29 pictures I do not know how to play games or do real things. Taylor went through a lot of emotional hell, and the tabloids ate it up.
Much like Taylor Lohan is going through quite the same ordeal, the difference Taylor had talent, and Lohan has lost her talent in the bars, or allegedly doing cocaine with her mother. While Taylor's personal demons affected her much more in her later years; she still won two Oscars, and had some of the most amazing performances in film. Lohan has tried to recoup but failed at hosting Saturday Night Live, which was a major foreshadowing of this film. Lohan's portrayal of Taylor was painful, and hilarious, but in the way Faye Dunaway portrayed Joan Crawford. Nothing is "convincing" about this conversion; she did not look like her, the make-up, and hair were bad, and she did Liz wrong. Apparently Ms. Lohan was a terror on the set, using the excuse she was trying to get in character; she needed to be an even bigger bitch apparently.
Grant Bowler is not without fault; he did played Richard Burton as an offish buffoon rather than the complicated drunk ladies man. Bowler has been suave and debonair in many different roles, like televisions Ugly Betty, in fact that should have influence his acting more, but he flat lined. Burton was just as complex as Liz, but he was beyond boring in this film.
Director Lloyd Kramer, and writer Christopher Monger had a gold mine in their lap. Lifetime was salivating at the tit, with the juicy material of the romance between Richard Burton and Elizabeth Taylor, but they struck out. They gambled with the wrong leading lady who should have tried to not play herself on screen, but rather capture the complicated person that was the beautiful/talented Elizabeth Taylor.